Engine lubricant

ABSTRACT

A lubricant composition includes: (a) one or more base oils, (b) at least one comb polymer formed by a polyalkyl(meth)acrylate main chain, and hydrocarbon side chains including at least 50 carbon atoms, (c) at least one nitrogen-containing organic friction modifier chosen from the optionally alkoxylated fatty amines, fatty amides or imides obtained by the condensation of fatty amines and carboxylic acids, alone or in a mixture, (d) optionally, one or more organometallic organomolybdenum-type friction modifiers. This is used for the lubrication of 4-stroke gasoline or diesel engines of light vehicles, preferentially of hybrid vehicles.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a National Phase Entry of International Application No. PCT/IB2011/053738, filed on Aug. 25, 2011, which claims priority to French Patent Application Serial No. 1056832, filed on Aug. 27, 2010, both of which are incorporated by reference herein.

TECHNICAL FIELD

A subject of the present invention is lubricant compositions for engines of gasoline vehicles or diesel vehicles, allowing a reduction in the fuel consumption of said vehicles.

BACKGROUND

Energy efficiency and reducing the fuel consumption of motor vehicle engines is a growing concern. It is known that the engine lubricants used in said vehicles play an important role in this regard. The energy losses due to friction between different engine components are produced, depending on the engine part, under regimes of either hydrodynamic and elastohydrodynamic, or limiting friction.

The choice of the bases and polymers improving the viscosity index (VI improver) has an influence on the losses under a hydrodynamic and elastohydrodynamic regime, while the choice of the friction modifiers influences the energy losses under limiting friction conditions. However, the formulation of a fuel-saving engine lubricant is not limited to the selection of these different components independently of each other. Account must be taken of the interactions between the different components, and the other performances of the lubricant, such as viscosity stability, corrosion inhibition, dispersing power etc. should not be changed.

Examples of engine lubricant formulas combining organometallic friction modifiers and/or various organic friction modifiers and VI improver polymers are known. Thus, engine lubricant compositions making it possible to achieve fuel economies (so-called “fuel eco” compositions) can be formulated by combining GTL-type bases with fatty acid ester- and polyol-type organic friction modifiers and polybutene-type VI improver polymers, ethylene propylene copolymers, polyacrylates or polymethacrylates, AB block copolymers obtained by the copolymerization of diene such as butadiene and isoprenes with vinyl aromatics such as styrene. Such compositions are for example disclosed in the application WO 2008/124191. Such bases however have the drawback of high cost and it is desirable to develop the use of additives making it possible to formulate fuel economy or fuel eco (FE) lubricants with predominantly conventional bases.

Organometallic friction modifiers can also be combined. The application EP 2078745 thus discloses a lubricant composition, for gasoline and diesel engines, combining molybdenum dithiocarbamates and zinc dithiophosphates, and making it possible to obtain fuel economies in the vehicles equipped with these engines. These formulas however contain high levels of sulphur, metals and phosphorus which can be prejudicial as regards particle emissions and post-treatment systems.

Fuel-eco engine lubricants comprising a mixture of organomolybdenum-type friction modifiers such as molybdenum dithiocarbamates, and organic friction modifiers such as fatty acid monoesters and polyols are described in the application WO 2004/053033. The application WO 93/21288 describes FE engine lubricants also combining ethoxylated amine-type friction modifiers with partial esters of fatty acids and polyols, and VI improvers of polyester, polymethacrylate, polyacrylate, polyolefin type. The application EP 0955353 also describes fuel-eco engine lubricant formulas combining organomolybdenum friction modifiers (MoDTC) with ethoxylated fatty amine-type organic friction modifiers, optionally in combination with VI improver polymers of polymethacrylate, polyolefin, styrene diene copolymer type.

The fuel economies achieved thanks to the engine lubricant have to be assessed overall, based on an entire standardized engine cycle representative of average conditions of use. However, a significant part of the energy losses occurs in the cold phase of the engine cycle, at start-up. This is particularly true for vehicles used in an urban setting, and in particular for the new hybrid vehicles which operate with a stop-start system, where the heat engine is stopped and restarted a significant number of times.

A need therefore exists for engine lubricants making it possible to achieve fuel economies greater than or equivalent to the existing formulas, and in particular over the cold phase of the engine cycle. The lubricant compositions according to the invention make it possible to achieve significant fuel economies, in particular in an urban cold cycle, thanks to a combination of VI improver polymers and specific friction modifiers.

SUMMARY

A subject of the present invention is a lubricant composition comprising:

(a) one or more base oils, (b) at least one comb polymer formed by a main polyalkyl(meth)acrylate chain, and hydrocarbon side chains comprising at least 50 carbon atoms, (c) at least one nitrogen-containing organic friction modifier chosen from the optionally alkoxylated fatty amines, the fatty amides or imides obtained by the condensation of fatty amines and carboxylic acids, alone or in a mixture, (d) optionally, one or more organometallic friction modifiers of the organomolybdenum type.

Preferentially, the hydrocarbon side chains of the comb polymers (b) are obtained by the polymerization or copolymerization of olefins, preferentially chosen from the optionally substituted styrenes, and comprising from 8 to 17 carbon atoms, 1,4 or 1,2 addition butadiene, or the monomers of formula (I)

where X1 and X2 are independently either hydrogen, or alkyl groups comprising from 1 to 18 carbon atoms.

According to an embodiment, the comb polymers (b) are obtained by the copolymerization of macromonomers of formula (II)

with acrylic or methacrylic monomers of formula (III):

where: each R′ is independently hydrogen or a methyl, R1 is an alkyl or aryl radical comprising from 1 to 6 carbon atoms, R2 is an alkyl radical comprising from 1 to 26 carbon atoms, A is formed by the 1,4 addition of butadiene, optionally substituted by alkyl groups comprising from 1 to 6 carbon atoms, or by the vinyl addition of styrene, optionally substituted by alkyl groups comprising from 1 to 6 carbon atoms, A′ is formed by the 1,2 addition of butadiene optionally substituted by alkyl groups comprising from 1 to 6 carbon atoms, or by the vinyl addition of styrene, optionally substituted by alkyl groups comprising from 1 to 6 carbon atoms, n and m are integers greater than or equal to zero, and n+m is an integer between 7 and 3000, preferentially between 10 and 3000.

According to another embodiment, the comb polymers (b) are obtained by the copolymerization of macromonomers of formula (IV):

with acrylic or methacrylic monomers of formula (II):

where: each R′ is independently hydrogen or a methyl, R1 is an alkyl or aryl radical comprising from 1 to 6 carbon atoms, R2 is an alkyl radical comprising from 1 to 26 carbon atoms, X1, X2, X3 are independently either hydrogen, or alkyl groups comprising from 1 to 18 carbon atoms, p, q, r are integers greater than or equal to zero, and p+q+r is an integer between 7 and 3000, preferentially between 10 and 3000.

According to an embodiment of the compositions according to the invention, at least one nitrogen-containing organic friction modifier (c) is chosen from the fatty amines of formula (V):

where R3, R4, R5 are independently either hydrogen or aliphatic chains comprising from 1 to 150 carbon atoms, preferentially from 1 to 32 carbon atoms, and at least one of the R3, R4, or R5 chains is a fatty aliphatic chain comprising at least 7 carbon atoms, n is an integer greater than or equal to 1, preferably comprised between 1 and 2.

According to another embodiment of the compositions according to the invention, at least one nitrogen-containing organic friction modifier (c) is chosen from the alkoxylated amines corresponding to formulae (VI) or (VII) below:

where R6 and R10 are, independently, fatty aliphatic chains, comprising between 7 and 150, preferentially between 7 and 32 carbon atoms, preferentially between 12 and 18 carbon atoms, R7 and R8 are, independently, hydrocarbon radicals comprising from 2 to 6 carbon atoms, preferentially from 2 to 4, preferentially 2 carbon atoms, R9 is a hydrocarbon radical comprising from 1 to 6 carbon atoms, x, y, p, q and z are integers between 0 and 50, complying with: 0<x+y<(or equal to) 50 and 0<p+q+z<(or equal to) 50.

Preferentially, when at least one nitrogen-containing organic friction modifier (c) is chosen from the ethoxylated amines, said friction modifier is chosen from the diethanolamines of formula (VIII):

where R11 is a fatty aliphatic chain comprising from 7 to 150 carbon atoms, preferentially from 7 to 32 carbon atoms, preferentially from 12 to 18 carbon atoms.

According to yet another embodiment of the compositions according to the invention, at least one nitrogen-containing organic friction modifier (c) is chosen from the fatty amides or imides obtained by the condensation of a dicarboxylic acid of formula (IX)

where R12 and R13 are independently hydrogen or a hydrocarbon group, or the R12 and R13 hydrocarbon groups form a ring, with an amine of formula (X) R14R15NH, where R14 and R15 represent independently hydrogen or an aliphatic chain comprising between 1 and 150 carbon atoms, preferentially from 1 to 32 carbon atoms, preferentially from 1 to 26 carbon atoms, and at least one of the R1 or R2 chains is a fatty aliphatic chain comprising at least 7 carbon atoms.

According to a preferred embodiment, the lubricant compositions according to the invention comprise at least one nitrogen-containing organic friction modifier (c) as described above and at least one organometallic friction modifier (d). Preferentially, in the lubricant compositions according to the invention containing organometallic friction modifiers (d), the latter are chosen from molybdenum dithiocarbamates, dithiophosphates, dithiophosphinates, xanthates and thioxanthates.

Preferentially, the organometallic friction modifier (d) is a molybdenum dithiocarbamate of formula (XI):

where R16, R17, R18, R19 are alkyl chains comprising from 8 to 13 carbon atoms.

Preferentially, the lubricant compositions according to the invention comprise:

from 65 to 90% by weight of one or more base oils (a),

from 2 to 15% by weight of polymer (b),

from 0.01 to 2% by weight of friction modifiers (c).

In a particularly preferred manner, the lubricant compositions according to the invention comprise at least one isoparaffinic mineral base oil (a) obtained by hydro-isomerization of an n-paraffin feedstock originating from solvent dewaxing or catalytic dewaxing, or at least one isoparaffin synthetic base oil (a) obtained by hydro-isomerization of an n-paraffin feedstock constituted by a Fischer Tropsch wax. According to an embodiment, the lubricant compositions according to the invention are of 0W20 or 0W30 grade according to the SAE J300 classification. According to a particularly preferred embodiment, the lubricant compositions according to the invention are oils for four-stroke gasoline or diesel engines of motor vehicles, preferentially of light vehicles, preferentially diesel. The present invention also relates to the use of lubricant compositions as described above for the lubrication of the 4-stroke gasoline or diesel engines of light vehicles, preferentially of hybrid vehicles. According to a preferred embodiment, this use is carried out in a diesel engine.

DETAILED DESCRIPTION

The lubricant compositions according to the invention make it possible to achieve fuel economies, in particular in a cold urban cycle, thanks to a specific combination of VI improver polymers and friction modifiers.

VI Improver Polymer (b):

The VI improver polymers are compounds making it possible to minimize variations in the viscosity range with temperature, i.e. making it possible to maintain a film of oil sufficient to protect the parts subject to friction at high temperature, and preventing too great an increase in viscosity when cold. The known viscosity index improvers are typically polyalkylmethacrylates (PMAs), polyacrylates, polyolefins, copolymers of olefins (dienes) with vinyl aromatics (styrene).

The U.S. Pat. Nos. 5,565,130 and 5,597,871 and the U.S. patent publication 2008/0194443 describe, as VI improver polymers, polymers having a comb structure (comb polymer), formed by the copolymerization of acrylate or methacrylate macromonomers comprising a hydrocarbon chain, for example of olefin-type copolymer, with acrylate or methacrylate monomers. Depending on whether the monomers are of acrylate or methacrylate type, these polymers are referred to as comb polyacrylates (comb PAs) or comb polymethacrylates (comb PMAs), respectively. According to the IUPAC Compendium of Chemical technology, 2^(nd) edition, 1997, a comb polymer is a polymer composed of comb macromolecules, which are macromolecules constituted by a main chain having multiple trifunctional branch points, each of which is the starting point for a linear side chain. This comb structure distinguishes the polymers of the U.S. Pat. Nos. 5,565,130 and 5,597,871 and U.S. patent publication 2008/0194443 from the polyacrylates and polymethacrylates (PMAs) usually utilized as VI improvers in the lubricant compositions of the prior art, in particular those described in the applications EP 0955353 and WO 93/21288. The lubricant compositions according to the invention include as polymer VI improver such a “comb polymer”, or polymer with a comb structure, as for example described in the U.S. Pat. Nos. 5,565,130 and 5,597,871, and the U.S. patent publication 2008/0194443 of the present application.

The lubricant compositions according to the invention contain therefore, as polymer VI improver, comb polyacrylates (comb Pas) or comb polymethacrylates (comb PMAs) which are comb polymers formed by a polyalkyl(meth)acrylate main chain, and long hydrocarbon side chains comprising at least 50 carbon atoms. Preferentially, these hydrocarbon side chains comprise between 50 and 25,000 carbon atoms, preferentially between 80 and 20,000 carbon atoms, typically of the order of 10,000 carbon atoms.

According to a preferred embodiment, the hydrocarbon side chains are obtained by the polymerization or copolymerization of olefins, for example styrene-type monomers, optionally substituted, and comprising from 8 to 17 carbon atoms, 1,4 or 1,2 addition butadiene, ethylene, propylene, isobutene and more generally monomers of formula (I):

where X1 and X2 are independently either hydrogen or alkyl groups comprising from 1 to 18 carbon atoms.

According to an embodiment, the compositions according to the invention contain a comb polymer obtained by the copolymerization of macromonomers of formula (II)

with acrylic or methacrylic monomers of formula (III):

where:

-   -   each R′ is independently hydrogen or a methyl,     -   R1 is an alkyl or aryl radical comprising from 1 to 6 carbon         atoms,     -   R2 is an alkyl radical comprising from 1 to 26 carbon atoms,     -   A is formed by the 1,4 addition of butadiene, optionally         substituted by alkyl groups comprising 1 to 6 carbon atoms, or         by the vinyl addition of styrene, optionally substituted by         alkyl groups comprising 1 to 6 carbon atoms,     -   A′ is formed by the 1,2 addition of butadiene optionally         substituted by alkyl groups comprising from 1 to 6 carbon atoms,         or by the vinyl addition of styrene, optionally substituted by         alkyl groups comprising 1 to 6 carbon atoms,     -   n and m are integers greater than or equal to zero, and n+m is         an integer between 7 and 3000, preferentially between 10 and         3000.

According to another embodiment, the compositions according to the invention contain a comb polymer obtained by the copolymerization of macromonomers of formula (IV):

with acrylic or methacrylic monomers of formula (III):

where: each R′ is independently hydrogen or a methyl, R1 is an alkyl or aryl radical comprising from 1 to 6 carbon atoms, R2 is an alkyl radical comprising from 1 to 26 carbon atoms, X1, X2, X3 are independently either hydrogen, or alkyl groups comprising from 1 to 18 carbon atoms, p, q, r are integers greater than or equal to zero, and p+q+r is an integer between 7 and 3000, preferentially between 10 and 3000.

In the compositions according to the invention, these comb polymers are advantageously used in combination with other VI improver polymers well known to a person skilled in the art. These well-known polymers are for example chosen from the category of the hydrogenated styrene diene copolymers, for example hydrogenated styrene butadiene copolymers (HSB) or styrene isoprene, which are well known to a person skilled in the art, preferentially hydrogenated styrene butadiene. The latter VI improver polymers, without influencing the fuel eco performances, however make it possible to provide the viscosity allowing formulation of grade 30 oils.

In the compositions according to the invention, the VI improver polymers (b) are typically present at levels comprised between 2 and 20% by mass with respect to the total weight of the composition, or also between 2 and 15%, or also between 5 and 15% by mass with respect to the total weight of the composition. When the polymers (b) are used in combination with other VI improver polymers, the total content of polymer VI improver is situated within the same ranges (between 2 and 20%, or between 2 and 15%, or between 5 and 15% by mass of the VI improver polymers with respect to the total weight of the composition).

Friction Modifiers:

Nitrogen-Containing Organic Friction Modifiers (c):

The nitrogen-containing organic friction modifiers of the compositions according to the invention are optionally alkoxylated fatty amines, or fatty amine derivatives of the amide or imide type obtained by the condensation of fatty amines with (di)carboxylic acids.

Fatty Amines:

The fatty amines used in the lubricants according to the present invention are primary, secondary or tertiary monoamines, or polyamines, comprising one or more fatty chains. The term fatty chain here denotes non-cyclic aliphatic hydrocarbon chains comprising at least 7 carbon atoms, saturated or unsaturated, optionally branched. The fatty amines are mainly obtained from the fatty acids (fatty-chain carboxylic acids), generally originating from the hydrolysis of the triglycerides present in vegetable and animal oils, such as copra, palm, olive, peanut, rapeseed, sunflower, soya, cotton or linseed oil, or beef tallow.

The fatty acids making it possible to obtain the fatty amines of the compositions according to the invention generally comprise from 7 to 32 carbon atoms, preferentially from 8 to 24 carbon atoms, preferentially from 10 to 20, preferentially from 12 to 18 carbon atoms. These are for example the caprylic, pelargonic, capric, undecylenque, lauric, tridecylenic, myristic, pentadecylic, palmitic, margaric, stearic, isostearic, nonadecylic, arachic, heneicosanoic, behenic, tricosanoic, lignoceric, pentacosanoic, cerotic, heptacosanoic, montanic, nonacosanoic, melissic, hentriacontanoic, laceroic acids or unsaturated fatty acids such as palmitoleic, oleic, erucic, nervonic, linoleic, a-linolenic, c-linolenic, di-homo-c-linolenic, arachidonic, eicosapentaenoic, docosahexanoic acids. These acids are dehydrated in the presence of ammonia in order to produce nitriles, which are then subjected to catalytic hydrogenation in order to produce primary, secondary or tertiary amines.

The fatty amines used as compound (c) in the lubricant compositions according to the invention correspond to general formula (V):

where R3, R4, R5 are independently either hydrogen or aliphatic chains comprising from 1 to 150 carbon atoms, preferentially from 1 to 32 carbon atoms, and at least one of the R3, R4 or R5 chains is a fatty aliphatic chain comprising at least 7 carbon atoms, n is an integer greater than or equal to 1, preferably comprised between 1 and 2.

The fatty amines used in the lubricants according to the invention are preferentially obtained from natural vegetable or animal resources. The treatments making it possible to arrive at fatty amines starting from natural oils can result in mixtures of primary, secondary and tertiary monoamines and polyamines.

Ethoxylated Amines:

As compound (c) in the lubricant compositions according to the invention, it is possible to use mono- or polyalkoxylated, for example mono or polyethoxylated, fatty amines obtained from the fatty amines described above. The alkoxylated amines used in the lubricant compositions according to the invention correspond for example to formulae (VI) and (VII) below:

where R6 and R10 are, independently, fatty aliphatic chains, comprising between 7 and 150, preferentially between 7 and 32 carbon atoms, preferentially between 12 and 18 carbon atoms, R7 and R8 are, independently, hydrocarbon radicals comprising from 2 to 6 carbon atoms, preferentially from 2 to 4, preferentially 2 carbon atoms, R9 is a hydrocarbon radical comprising from 1 to 6 carbon atoms, x, y, p, q and z are integers between 0 and 50 complying with: 0<x+y<(or equal to) 50 and 0<p+q+z<(or equal to) 50.

Preferentially, R5 and R9 are aliphatic fatty chains, optionally substituted by aryl groups. In a particularly preferred manner, they comprise between 7 and 30 carbon atoms, preferentially between 10 and 20, preferentially between 12 and 18 carbon atoms. Preferentially, R6 and R7 are aliphatic, preferentially alkyl, chains comprising from 2 to 6 carbon atoms, preferentially from 2 to 4, preferentially 2 carbon atoms. Preferentially, R8 is an aliphatic, preferentially alkyl, chain comprising from 1 to 6 carbon atoms, preferentially from 2 to 4, preferentially 3 carbon atoms.

Particularly preferred compounds are the diethanolamines of formula (VIII):

where R11 is an aliphatic chain comprising from 7 to 150 carbon atoms, preferentially from 7 to 32 carbon atoms, preferentially from 12 to 18 carbon atoms

Fatty Amides and Imides:

The nitrogen-containing organic friction modifiers (c) of the lubricant compositions according to the invention can be amides or imides obtained by the condensation of the fatty amines described above and carboxylic acids, such as for example the oleylamides, in particular primary oleylamides. According to an embodiment, the organic friction modifiers (c) are amides or imides obtained by the condensation of fatty amines and dicarboxylic, aliphatic or aromatic acids, optionally hydroxylated, such as for example malonic, succinic, malic, tartaric, phthalic, isophthalic acids, preferentially tartaric acid.

According to an embodiment, the organic friction modifiers (c) are fatty amides or imides obtained by the condensation of a dicarboxylic acid of formula (IX)

where R12 and R13 are independently hydrogen or a hydrocarbon group, or the hydrocarbon groups R12 and R13 form a ring, with an amine of formula (X) R14R15NH where R14 and R15 represent independently hydrogen or an aliphatic chain comprising between 1 and 150 carbon atoms, preferentially from 1 to 32 carbon atoms, preferentially from 1 to 26 carbon atoms, and at least one of the R1 or R2 chains is a fatty aliphatic chain comprising at least 7 carbon atoms.

Such friction modifiers are described in the U.S. patent publication 2006/0079413, paragraphs [0025] to [028].

Organometallic Friction Modifiers (d):

Optionally, the lubricant compositions according to the invention can contain one or more organomolybdenum compounds as friction modifiers. These compounds are well known to a person skilled in the art. These are for example compounds also containing sulphur or phosphorus, such as molybdenum dithiophosphates, dithiocarbamates, dithiophosphinates, xanthates, thioxanthates. Organomolybdenum compounds suitable for the lubricant compositions according to the present invention are for example described in the application EP 2 078 745, [0036] to [062].

In the compositions according to the invention, the nitrogen-containing organic friction modifiers (c) are typically present at levels comprised between 0.01 and 2% by mass with respect to the total weight of the composition, or also between 0.1 and 1%, or also between 0.3 and 0.8% by mass with respect to the total weight of the composition. When the nitrogen-containing organic friction modifiers (c) are used in combination with other organometallic friction modifiers, (d), the total content of friction modifiers is situated in the same ranges (between 0.01 and 2%, or between 0.1 and 1%, or between 0.5 and 0.8% by mass of the friction modifiers with respect to the total weight of the composition).

Base Oils (a):

The lubricant compositions according to the present invention include one or more base oils, generally representing at least 60% by weight of the lubricant compositions, generally at least 65% by weight, and possibly ranging up to 90% and more. The base oil or oils used in the compositions according to the present invention can be oils of mineral or synthetic origin of groups I to V according to the classes defined in the API classification (or their equivalents according to the ATIEL classification) as summarized below, alone or in a mixture.

Saturates content Sulphur content Viscosity index Group I mineral oils <90% >0.03% 80 ≦ VI < 120 Group II hydrocracked oils ≧90% ≦0.03% 80 ≦ VI < 120 Group III ≧90% ≦0.03% ≧120 hydrocracked or hydro- isomerized oils Group IV PAO Polyalphaolefins Group V Esters and other bases not included in bases of groups I to IV

These oils can be oils of vegetable, animal, or mineral origin. The mineral base oils according to the invention include all types of bases obtained by atmospheric and vacuum distillation of crude oil, followed by refining operations such as solvent extraction, deasphalting, solvent dewaxing, hydrotreatment, hydrocracking and hydroisomerization, hydrofinishing.

The base oils of the compositions according to the present invention can also be synthetic oils, such as certain esters of carboxylic acids and alcohols, or polyalphaolefins. The polyalphaolefins used as base oils are for example obtained from monomers having 4 to 32 carbon atoms (for example octene, decene), and have a viscosity at 100° C. comprised between 1.5 and 15 Cst. Their weight-average molecular mass is typically comprised between 250 and 3000.

Mixtures of synthetic and mineral oils can also be used. Preferentially, the lubricant compositions according to the invention are formulated with bases of group III and/or IV.

According to a preferred embodiment, the lubricant compositions according to the invention include at least one isoparaffinic mineral base oil, obtained by hydro-isomerization of an n-paraffin feedstock, originating from solvent dewaxing or catalytic dewaxing operations. Such bases are mineral bases of group III referred to as group III+ bases. According to another preferred embodiment, the lubricant compositions according to the invention include at least one synthetic isoparaffinic base oil, obtained by the hydro-isomerization of an n-paraffin feedstock such as a Fischer Tropsch wax. According to a particularly preferred embodiment, the lubricant compositions according to the invention contain 65 to 90% by weight of such isoparaffinic bases. According to an embodiment, the lubricant compositions according to the invention contain exclusively so-called group III+ mineral bases or bases obtained by the hydro-isomerization of a Fischer Tropsch wax as base oil, in a proportion comprised between 65 and 90% by mass.

Preferably, the compositions according to the present invention have a kinematic viscosity at 100° C. comprised between 5.6 and 16.3 Cst measured by the standard ASTM D445, (SAE grade 20, 30 and 40), preferentially comprised between 9.3 and 12.5 Cst (grade 30). According to a particularly preferred embodiment, the compositions according to the present invention are multigrade oils of grade 0W30 or 0W20 according to the SAE J300 classification. The compositions according to the present invention also preferably have a viscosity index VI greater than 130, preferentially greater than 150, preferentially greater than 160. Preferentially, the lubricant compositions according to the invention are engine oils for gasoline or diesel vehicles, preferentially for diesel vehicles, preferentially according to the specifications ACEA C2 or JASO DL1 well known to a person skilled in the art.

Other Additives:

The lubricant compositions according to the invention can also contain all types of additives suited to their use. These additives can be added individually, or in the form of packages of additives, guaranteeing a certain level of performance to the lubricant compositions, as required, for example for an ACEA (European Automobile Manufacturers Association) or JASO (Japan Automobile Standards Organization) diesel lubricant. These are given by way of example and non-limitatively:

Dispersants, generally representing between 5 and 8% by weight of the lubricant compositions. The dispersants such as for examples succinimides, PIB (polyisobutene) succinimides, Mannich bases ensure that the insoluble solid contaminants constituted by the secondary oxidation products formed when the engine oil is in service are maintained in suspension and removed.

Antioxidants, generally representing between 0.5 and 2% by weight of the lubricant compositions. The antioxidants slow down the degradation of the oils in service, a degradation which can result in the formation of deposits, the presence of sludge, or an increase in the viscosity of the oil. They act as radical inhibitors or hydroperoxide destroyers. Among the antioxidants commonly used are found the phenolic type antioxidants and sterically hindered amines. Another class of antioxidants is that of the oil-soluble copper compounds, for examples copper thio- or dithiophosphates, salts of copper and carboxylic acids, copper dithiocarbamates, sulphonates, phenates, acetylacetonates. Copper I and II salts of succinic acid or anhydride are used.

Anti-wear additives, generally representing between 1 and 2% by weight of the lubricant compositions. The anti-wear additives protect the friction surfaces by the formation of a protective film adsorbed on these surfaces. The most commonly used is zinc dithiophosphate or DTPZn. Also found in this category are various phosphorus-, sulphur-, nitrogen-, chlorine- and boron-containing compounds.

Detergents, generally representing between 2 and 4% by weight of the lubricant compositions. The detergents are typically alkali or alkaline-earth metal salts of carboxylic acids, sulphonates, salicylates, naphthenates, as well as phenate salts. They typically have a BN according to ASTM D2896 greater than 40 or 80 mg KOH/gram of detergent, and are most often overbased, with BN values typically of the order of 150 and more, or even 250 or 400 or more (expressed in mg of KOH per gram of detergent).

And also antifoaming agents, pour point depressants, corrosion inhibitors, etc.

EXAMPLES

Preparation of the Oils:

Several oils for diesel engine vehicles, of grade 0W30, were prepared from a package of performance additives for diesel engine oils making it possible to meet the ACEA C2/JASO DL1 specifications, and comprising antioxidants, corrosion inhibitors, dispersants, detergents, anti-wear agents, pour point depressants and corrosion inhibitors.

The compositions (in % by mass) of these oils are given in Table 1 below:

TABLE 1 compositions by mass of the engine oils of grade 0W30 A B C D E F Group III+ 79.2 73.0 72.7 — — 79.9 base Synthetic base — — — 72.8 72.3 — Additives 11.9 12.2 12.2 12.2 12.2 12.4 package Pour point — — — 0.2 0.2 — depressant SBH 2.6 14.3 14.3 13.5 14.8 — Comb PMA 5.8 — — — — — PMA 6.7 Fatty amides 0.5 0.5 0.5 0.5 0.5 1 and imides of tartaric acid MoDTC — 0.3 0.3 — — (Mo ppm) (300 ppm) (300 ppm) Total 100.0 100.0 100.0 100.00 100.00 100.00

Fuel Consumption Measurement:

Engine tests have made it possible to evaluate the fuel economies achieved on a diesel engine vehicle, the engine of which is lubricated with these different oils. 5W30 oil, comprising an additives package with a performance level ACEA Cl/ASO DL1, a VI improver polymer of hydrogenated polyisoprene type and formulated from group III base oils, serves as a reference for the test.

Principle of the Test:

A Toyota Corolla Verso D4D Clean Power vehicle, equipped with a Common Rail injection 2AD engine, a DPNR (Diesel Particulate-Nox reduction) post-treatment system with a 5^(th) injector regeneration trap, placed in a B7 environment, is subjected to an NEDC standardized driving cycle (New European Driving Cycle), also called an MVEG (Motor Vehicle Emissions group) cycle. This cycle is designed to reproducibly imitate the conditions encountered on European roads and is widely used to measure the vehicles' fuel consumption and pollutant emissions. The characteristics of this cycle (speed as a function of time) are given in FIG. 1. It comprises a cold phase or cold urban phase (from 0 to 200 seconds), an intermediate phase or hot urban phase (from 200 to 725 seconds), a hot phase or extra urban phase (from 725 to 1200 seconds).

Implementation:

The vehicle is placed on a double roller dynamometer meeting E4 standards making it possible to reproducibly simulate the on-road resistance encountered due to the aerodynamic drag and mass of the vehicle. The tests are carried out at an ambient air temperature of 20° C., 50% humidity and pressure of 1000 mbar. The consumption is calculated on the basis of carbon accounting after analysis of the exhaust gas. The fuel used for all the tests is an EN590-B7 gasoil.

Results:

The absolute fuel consumptions are measured (in litres/100 km), over the whole cycle and by phase. The differences in consumption (in %) relative to the reference taken immediately before the oil sample to be analyzed are also calculated. The results are given in Table 2.

Oil A is in accordance with the invention. It contains as friction modifier a mixture of fatty amides and imides of tartaric acid. It contains as VI improver comb polymer PMA, and a smaller quantity of SBH, intended to provide the viscosity necessary in order to obtain a grade 30 oil.

Oils B to F contain friction modifiers identical to the oils according to the invention, at comparable levels, but are formulated without comb polymer. The quantities of VI improver polymer are adjusted in order to obtain the desired viscosimetric grade.

Oil A according to the invention makes it possible to achieve fuel economies relative to oils B, C, D, E, F, throughout the engine cycle and in particular in the cold phase and the intermediate phase.

TABLE 2 fuel consumptions Cold phase Intermediate phase Previous Difference/ Previous Difference/ reference previous reference previous consumption consumption reference consumption consumption reference A 261 B 9.08 9.74 6.77% 7.97 8.25 3.39% B 53 C 9.62 9.74 1.23% 8.21 8.25 0.48% C 53 D 9.39 9.71 3.29% 8.01 8.14 1.59% D 130 mix 9.49 9.73 2.46% 8.18 8.38 2.38% E 130 9.43 9.71 2.88% 8.17 8.32 1.80% F G09- 9.36 9.71 3.60% 8.25 8.32 0.84% 0052C Hot phase Complete cycle Previous Difference/ Previous Difference/ reference previous reference previous consumption consumption reference consumption consumption reference A 261 B 5.74 5.81 1.20% 6.67 6.86 2.77% B 53 C 5.94 5.81 −2.23% 6.92 6.86 −0.87% C 53 D 5.73 5.84 1.88% 6.71 6.85 2.04% D 130 mix 5.75 5.81 1.03% 6.78 6.90 1.74% E 130 5.76 5.78 0.34% 6.78 6.86 1.16% F G09- 5.78 5.78 0.00% 6.81 6.86 0.73% 0052C 

1. A lubricant composition comprising: (a) one or more base oils; (b) at least one comb polymer formed by a polyalkyl(meth)acrylate main chain, and hydrocarbon side chains comprising at least 50 carbon atoms; and (c) at least one nitrogen-containing organic friction modifier chosen from fatty amines, alkoxylated fatty amines, fatty amides or imides obtained by the condensation of fatty amines and carboxylic acids, alone or in a mixture.
 2. The lubricant composition according to claim 1 where the hydrocarbon side chains of the comb polymers (b) are obtained by the polymerization or copolymerization of olefins.
 3. The lubricant composition according to claim 1 where the comb polymers (b) are obtained by the copolymerization of macromonomers of formula (II)

with acrylic or methacrylic monomers of formula (III):

where: each R′ is independently hydrogen or a methyl, R1 is an alkyl or aryl radical comprising from 1 to 6 carbon atoms, R2 is an alkyl radical comprising from 1 to 26 carbon atoms, A is formed by the 1,4 addition of butadiene, optionally substituted by alkyl groups comprising 1 to 6 carbon atoms, or by the vinyl addition of styrene, optionally substituted by alkyl groups comprising 1 to 6 carbon atoms, and A′ is formed by the 1,2 addition of butadiene optionally substituted by alkyl groups comprising 1 to 6 carbon atoms, or by the vinyl addition of styrene, optionally substituted by alkyl groups comprising 1 to 6 carbon atoms, n and m are integers greater than or equal to zero, and n+m is an integer between 7 and
 3000. 4. The lubricant composition according to claim 1 where the comb polymers (b) are obtained by the copolymerization of macromonomers of formula (IV):

with acrylic or methacrylic monomers of formula (III):

where: each R′ is independently hydrogen or a methyl, R1 is an alkyl or aryl radical comprising from 1 to 6 carbon atoms, R2 is an alkyl radical comprising from 1 to 26 carbon atoms, X1, X2, X3 are independently either hydrogen, or alkyl groups comprising from 1 to 18 carbon atoms, and p, q, r are integers greater than or equal to zero, and p+q+r is an integer between 7 and
 3000. 5. The lubricant composition according to claim 1 where at least one nitrogen-containing organic friction modifier (c) is chosen from the fatty amines of formula (V):

where R3, R4, R5 are independently either hydrogen or aliphatic chains comprising from 1 to 150 carbon atoms, and at least one of the R3, R4, or R5 chains is a fatty aliphatic chain comprising at least 7 carbon atoms, and n is an integer greater than or equal to
 1. 6. The lubricant composition according to claim 1 where at least one nitrogen-containing organic friction modifier (c) is chosen from the alkoxylated amines corresponding to formulae (VI) or (VII) below:

where R6 and R10 are, independently, fatty aliphatic chains, comprising between 7 and 150, R7 and R8 are, independently, hydrocarbon radicals comprising from 2 to 6 carbon atoms, R9 is a hydrocarbon radical comprising from 1 to 6 carbon atoms, and x, y, p, q and z are integers between 0 and 50, complying with: 0<x+y<(or equal to) 50 and 0<p+q+z<(or equal to)
 50. 7. The lubricant composition according to claim 6 where at least one nitrogen-containing organic friction modifier (c) is chosen from the diethanolamines of formula (VIII):

where R11 is a fatty aliphatic chain comprising from 7 to 150 carbon atoms.
 8. The lubricant composition according to claim 1 where at least one nitrogen-containing organic friction modifier (c) is chosen from the fatty amides or imides obtained by the condensation of a dicarboxylic acid of formula (IX)

where R12 and R13 are independently hydrogen or a hydrocarbon group, or the R12 and R13 hydrocarbon groups form a ring, with an amine of formula (X) R14R15NH, and where R14 and R15 represent independently hydrogen or an aliphatic chain comprising between 1 and 150 carbon atoms and at least one of the R1 or R2 chains is a fatty aliphatic chain comprising at least 7 carbon atoms.
 9. The lubricant composition according to claim 1 comprising at least one nitrogen-containing organic friction modifier (c) and at least one organometallic friction modifier (d).
 10. The lubricant composition according to claim 9 where the organometallic friction modifiers (d) are chosen from molybdenum dithiocarbamates, dithiophosphates, dithiophosphinates, xanthates, thioxanthates.
 11. The lubricant composition according to claim 10 where the organometallic friction modifier (d) is a molybdenum dithiocarbamate of formula (XI):

where R16, R17, R18, R19 are alkyl chains comprising from 8 to 13 carbon atoms.
 12. The lubricant composition according to claim 8 comprising: from 65 to 90% by weight one or more base oils (a); from 2 to 15% by weight polymer (b); and from 0.01 to 2% by weight friction modifiers (c).
 13. The lubricant composition according to claim 1 comprising at least one isoparaffinic mineral base oil (a) obtained by hydro-isomerization of an n-paraffin feedstock originating from solvent dewaxing or catalytic dewaxing, or at least one isoparaffinic synthetic base oil (a) obtained by hydro-isomerization of an n-paraffin feedstock constituted by a Fischer Tropsch wax.
 14. The lubricant composition according to claim 1 which is of grade 0W20 or 0W30 according to the SAE J300 classification.
 15. A method of lubricating a 4-stroke gasoline or diesel engines of light with a lubricant composition comprising: (a) one or more base oils; (b) at least one comb polymer formed by a polyalkyl(meth)acrylate main chain, and hydrocarbon side chains comprising at least 50 carbon atoms; and (c) at least one nitrogen-containing organic friction modifier chosen from fatty amines, alkoxylated fatty amines, fatty amides or imides obtained by the condensation of fatty amines and carboxylic acids, alone or in a mixture, (d) one or more organometallic organomolybdenum-type friction modifiers vehicles.
 16. The method according to claim 15 wherein the diesel engine is lubricated with the lubricant composition.
 17. The lubricant composition according to claim 5 wherein the nitrogen-containing organic friction modifier (c) is chosen from the fatty amines of formula (V):

where R3, R4, R5 are independently either hydrogen or aliphatic chains comprising from 1 to 32 carbon atoms and at least one of the R3, R4, or R5 chains is a fatty aliphatic chain comprising at least 7 carbon atoms, and n is an integer greater than or equal to
 1. 18. The lubricant composition according to claim 6 wherein the nitrogen-containing organic friction modifier (c) is chosen from the alkoxylated amines corresponding to formulae (VI) or (VII) below:

where R6 and R10 are, independently, fatty aliphatic chains, comprising between 7 and 32, R7 and R8 are, independently, hydrocarbon radicals comprising from 2 to 6 carbon atoms, R9 is a hydrocarbon radical comprising from 1 to 6 carbon atoms, and x, y, p, q and z are integers between 0 and 50, complying with: 0<x+y<(or equal to) 50 and 0<p+q+z<(or equal to)
 50. 19. The lubricant composition according to claim 7 where at least one nitrogen-containing organic friction modifier (c) is chosen from the diethanolamines of formula (VIII):

where R11 is a fatty aliphatic chain comprising from 7 to 32 carbon atoms.
 20. The lubricant composition according to claim 2 wherein the olefins are selected from the group consisting of the styrenes comprising from 8 to 17 carbon atoms, the substituted styrenes comprising from 8 to 17 carbon atoms, 1,4 or 1,2 addition butadiene, or the monomers of formula (I):

wherein X1 and X2 are independently either hydrogen, or alkyl groups comprising from 1 to 18 carbon atoms. 